1. Field of the Invention
The present invention relates to a semiconductor device and method of manufacture thereof, a circuit board, and an electronic instrument.
2. Description of Related Art
With the recent increasingly compact nature of electronic instruments, there is a demand for semiconductor device packages appropriate for high-density mounting. In response to this, surface-mounted packages have been developed, such as Ball Grid Array (BGA) and Chip Scale/Size Package (CSP). With such surface-mounted packages, a substrate is often used on which a wiring pattern for connection to the semiconductor chip is formed. Penetrating holes are formed in the substrate, and external electrodes are often formed so as to project through these penetrating holes from the surface opposite to that of the wiring pattern.
With a semiconductor device to which a package of this construction is applied, after mounting on the circuit board, because of the difference in coefficient of thermal expansion between the circuit board and semiconductor device, a stress may be applied to the external electrodes, and cracks may form in the external electrodes.
The present invention solves these problems, and has as its object the provision of a semiconductor device and method of manufacture thereof, a circuit board, and an electronic instrument such that cracks in the external electrodes can be prevented.
(1) According to a first aspect of the present invention, there is provided a semiconductor device comprising:
a substrate in which penetrating holes are formed;
a semiconductor chip having electrodes;
a conductive member adhered on one side of the substrate by an adhesive material over a particular region of the one side including the penetrating holes, and electrically connected to the electrodes of the semiconductor chip on the side opposite to the surface of being adhered by the adhesive; and
external electrodes which are provided through the penetrating holes, electrically connected to the conductive member, and extending as far as outside of the other side of the substrate;
wherein a part of the adhesive material is interposed between internal wall surfaces forming the penetrating holes and the external electrodes within the penetrating holes.
According to the present invention, external electrodes are formed within penetrating holes, and between the external electrodes and penetrating holes part of an adhesive material is interposed. Therefore, since the adhesive material forms a stress absorption material, stress caused by differences in the coefficient of thermal expansion with the circuit board (thermal stress) and mechanical stress applied to the circuit board from the outside can be absorbed. In this way, the occurrence of cracks in the external electrodes can be prevented.
It should be noted that in the present invention, the adhesive material may be continuous from between the substrate and conductive member to the internal wall surfaces of the penetrating holes, or may exist discontinuously within the penetrating holes.
(2) In this semiconductor device, a part of the adhesive material may enter and exist within the penetrating holes.
(3) According to a second aspect of the present invention, there is provided a semiconductor device comprising:
a substrate in which penetrating holes are formed;
a semiconductor chip having electrodes;
a conductive member directly formed over a particular region including the penetrating holes on one side of the substrate, and electrically connected to the electrodes of the semiconductor chip; and
external electrodes which are provided through the penetrating holes, electrically connected to the conductive member, and extending as far as outside of the other side of the substrate;
wherein the substrate is formed of a material of a higher elasticity than the external electrodes; and
wherein protrusions are formed in the internal wall surfaces of the penetrating holes by the material constituting the substrate.
According to the present invention, since protrusions are formed in the internal wall surfaces of the penetrating holes, deformation is easier than with flat internal wall surfaces. Therefore, stress caused by differences in the coefficient of thermal expansion with the circuit board (thermal stress) and mechanical stress applied to the circuit board from the outside can be absorbed. In this way, the occurrence of cracks in the external electrodes can be prevented.
(4) Each of the external electrodes may include a base portion positioned within each of the penetrating holes and a projecting portion projecting from each of the penetrating holes, the diameter d of the base portion being related to the diameter xcfx86 of the projecting portion by xcfx86xe2x89xa6d.
By this means, the diameter of the external electrode is not squeezed by the penetrating hole, and no necking occurs. Therefore, stress caused by differences in the coefficient of thermal expansion with the circuit board (thermal stress) and mechanical stress applied from outside the circuit board is not concentrated, and the occurrence of cracks in the external electrodes can be prevented.
(5) According to a third aspect of the present invention, there is provided a semiconductor device comprising:
a substrate in which penetrating holes are formed;
a semiconductor chip having electrodes;
a conductive member adhered on one side of the substrate by an adhesive material over a particular region of the one side including the penetrating holes, and electrically connected to the electrodes of the semiconductor chip on the side opposite to the surface of being adhered by the adhesive; and
external electrodes which are provided through the penetrating holes, electrically connected to the conductive member, and extending as far as outside of the other side of the substrate;
wherein each of the external electrodes includes a base portion positioned within each of the penetrating holes and a projecting portion projecting from each of the penetrating holes, the diameter d of the base portion being related to the diameter xcfx86 of the projecting portion by xcfx86xe2x89xa6d.
According to the present invention, external electrodes are formed within penetrating holes. The diameter d of the base portion of the external electrodes is related to the diameter xcfx86 of the projecting portion by xcfx86xe2x89xa6d. In other words, the diameter of the external electrodes is not squeezed by the penetrating holes, and no necking occurs. Therefore, stress caused by differences in the coefficient of thermal expansion with the circuit board (thermal stress) and mechanical stress applied from outside the circuit board is not concentrated, and the occurrence of cracks in the external electrodes can be prevented.
(6) The substrate may be an insulating substrate.
(7) The substrate may be a printed substrate.
(8) The external electrodes may be formed of solder.
(9) The outline form of the substrate may be larger than the semiconductor chip outline form.
(10) The electrodes of the semiconductor chip may be electrically connected to the conductive member through an anisotropic conductive material having conductive particles dispersed in an adhesive.
(11) The electrodes of the semiconductor chip may be electrically connected to the conductive member through wires.
(12) According to a fourth aspect of the present invention, there is provided a circuit board on which the above described semiconductor device is mounted.
(13) According to a fifth aspect of the present invention, there is provided an electronic instrument having the above described circuit board.
(14) According to a sixth aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising:
a step of providing a substrate with an adhesive material provided on one surface thereof;
a step of carrying out punching from the side of the substrate on which the adhesive material is provided, and in the direction of the opposite side thereof, whereby penetrating holes are formed and a part of the adhesive material is drawn into the penetrating holes;
a step of adhering a conductive member over a particular region on the one surface including the penetrating holes on the substrate through the adhesive material;
a step of providing a material for forming external electrodes on the conductive member, and forming external electrodes through the penetrating holes and the inner side of the part of adhesive material drawn into the penetrating holes to project from the surface opposite to the surface of the substrate on which the conductive member is formed; and
a step of electrically connecting electrodes of a semiconductor chip to the conductive member.
According to the present invention, when the substrate is punched and the penetrating holes are formed, at the same time part of the adhesive material can be drawn into the penetrating holes. When the external electrodes are formed through the penetrating holes, this part of the adhesive material is interposed between the external electrodes and penetrating holes. With the thus obtained semiconductor device, the adhesive material acts as a stress absorption material, and therefore stress caused by differences in the coefficient of thermal expansion with the circuit board (thermal stress) and mechanical stress applied from outside the circuit board is absorbed, and the occurrence of cracks in the external electrodes can be prevented.
(15) According to a seventh aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising:
a step of providing a substrate of a material of a higher elasticity than external electrodes, having penetrating holes in which the internal wall surfaces have protrusions, and having a conductive member directly formed over a region including the penetrating holes;
a step of providing a material for forming external electrodes on the conductive member, and forming external electrodes through the penetrating holes to project from the surface opposite to the surface of the substrate on which the conductive member is formed; and
a step of electrically connecting electrodes of a semiconductor chip to the conductive member.
According to the present invention, since protrusions are formed in the internal wall surfaces of the penetrating holes, deformation is easier than with flat internal wall surfaces. Therefore stress caused by differences in the coefficient of thermal expansion with the circuit board (thermal stress) and mechanical stress applied to the circuit board from the outside can be absorbed. In this way, the occurrence of cracks in the external electrodes can be prevented.
(16) The method of manufacturing the semiconductor device may further comprise a step of punching the substrate before the conductive member is formed, wherein a part of the substrate is drawn into the penetrating holes and the protrusions are formed.
By this means, in the step of punching, the protrusions can be formed simply.
(17) In this method of manufacture, the penetrating holes may be formed by a laser.
When a laser is used, the protrusions occur naturally.
(18) In this method of manufacture, the penetrating holes may be formed by wet etching.
When wet etching is applied, the protrusions occur naturally.
(19) In this method of manufacture, wherein each of the external electrodes includes a base portion positioned within each of the penetrating holes and a projecting portion projecting from each of the penetrating holes, the diameter d of the base portion being related to the diameter xcfx86 of the projecting portion by xcfx86xe2x89xa6d.
By this means, the diameter of the external electrodes is not squeezed by the penetrating holes, and no necking occurs. Therefore, stress caused by differences in the coefficient of thermal expansion with the circuit board (thermal stress) and mechanical stress applied from outside the circuit board is not concentrated, and the occurrence of cracks in the external electrodes can be prevented.
(20) According to an eighth aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising:
a step of providing a substrate in which penetrating holes are formed and a conductive member is formed over a region including the penetrating holes;
a step of providing a material for forming external electrodes on the conductive member, and forming external electrodes through the penetrating holes to project from the surface opposite to the surface of the substrate on which the conductive member is formed; and
a step of electrically connecting electrodes of a semiconductor chip to the conductive member;
wherein each of the external electrodes includes a base portion positioned within each of the penetrating holes and a projecting portion projecting from each of the penetrating holes, the diameter d of the base portion being related to the diameter xcfx86 of the projecting portion by xcfx86xe2x89xa6d.
With a semiconductor device fabricated according to the present invention, the diameter d of the base portion of the external electrodes is related to the diameter xcfx86 of the projecting portion by xcfx86xe2x89xa6d. In other words, the diameter of the external electrodes is not squeezed by the penetrating holes, and no necking occurs. Therefore, stress caused by differences in the coefficient of thermal expansion with the circuit board (thermal stress) and mechanical stress applied from outside the circuit board is not concentrated, and as a result the occurrence of cracks in the external electrodes can be prevented.
(21) The substrate may be either of an insulating film and a printed substrate.
(22) The material for forming external electrodes may be solder.
(23) The method of manufacturing a semiconductor device may further comprise a step of punching the substrate around the semiconductor chip, after the step of electrically connecting electrodes of the semiconductor chip to the conductive member.
(24) In the step of electrically connecting the electrodes of the semiconductor chip to the conductive member, the electrodes may be connected to the conductive member through an anisotropic conductive material having conductive particles dispersed in an adhesive.
(25) In the step of electrically connecting the electrodes of the semiconductor chip to the conductive member, the electrodes may be connected to the conductive member through wires.